docs: def _truncateend(self, bits):
          """Truncate bits from the end of the bitstring."""
          assert 0 <= bits <= self.len
          if not bits:
              return
          if bits == self.len:
              self._clear()
              return
          newlength_in_bytes = (self._offset + self.len - bits + 7) // 8
          self._setbytes_unsafe(self._datastore.getbyteslice(0, newlength_in_bytes), self.len - bits,
                                self._offset)
          assert self._assertsanity()